Wireless communication channels such as wireless fidelity (WiFi), cellular, sub-6 (gigahertz) GHz spectrum for fifth generation wireless systems (5G), etc., need good power amplifier (PA), low-noise amplifier (LNA), switch, CMOS logic, and filters. Known designs use multi-chip solutions including complimentary-metal-oxide semiconductor (CMOS), radio frequency complimentary-metal-oxide semiconductor (RFCMOS), BiCMOS, gallium arsenide (GaAs), GaN, filters, etc. However, known acoustic filters using layers of GaN show poor quality (Q) and electromechanical coupling coefficient (k2eff).
A known bulk acoustic wave (BAW) filter on a silicon (Si) substrate is depicted in FIGS. 1A, 1B, and 1C. FIGS. 1A and 1B schematically illustrate cross-sectional views along the cut lines 1A-1A′ and 1B-1B′ of FIG. 1C, and FIG. 1C is a top view. Referring to FIGS. 1A, 1B, and 1C, a BAW filter 101 including a bottom electrode 103, an aluminum nitride (AlN) acoustic layer 105, and a top electrode 107 is formed over a Si substrate 109. The known structure also includes vias 111 through the AlN layer 105 and a cavity 113 in a portion of the Si substrate 103 under respective portions of the bottom electrode 103 and the AlN layer 105. Further, the known structure includes a liner 115 and a metal contact 117 through the AlN layer 105 down to the bottom electrode 103 and a second metal contact 119 on a portion of the top electrode 107. This BAW filter 101; however, does not include a GaN channel or a GaN PA.
A need therefore exists for methodology enabling formation of an integrated acoustic filter, GaN PA, and CMOS with high Q and coupling k2eff and the resulting device.